Optical transmission system constructing method and system

ABSTRACT

An optical transmission system accomplishes optical transmission to a long distance by combining a multiplexing line terminal with optical amplifiers, linear repeaters, and regenerators with optical amplifiers combined together. The system also accomplishes the optical transmission to a short distance by directly connecting the linear terminals therebetween, with an electric-to-optic converter replaced by an electric-to-optic converter having a semiconductor amplifier, with an optic-to-electric converter by an optic-to-electric converter having an avalanche photodiode as light receiver, an with no use of any optical booster amplifier and optical preamplifier in the multiplexing line terminal. With these, the optical transmission system can be easily constructed depending on the transmission distance required.

This is a divisional of application Ser. No. 08/044,425 filed 7 Apr.1993, U.S. Pat. No. 5,55,477, which is a continuation in part ofapplication Ser. No. 08/023,546 filed 26 Feb. 1993, U.S. Pat. No.5,500,756 issued 19 Mar. 1996.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an optical transmission method andsystem for carrying data transmission with the use of optical fiber.More particularly, it concerns an optical transmission method and systempreferable in high-speed data transmission over a long distance.

2. Description of the Related Art

Prior art related to the optical transmission system includes, forexample, the technique disclosed in the Japanese Patent ApplicationLaid-Open 3-296334.

However, it is demanded to accomplish an optical transmission systemoperating at further higher speed since development of the moderninformation society has increased long-distance communication traffic inrecent years. Also, it is desired that the optical transmission systemcan transmit data even longer distances without repeaters to increasereliability and decrease cost of the system. development of theinformation society. For this reason, it is needed to achieve an opticaltransmission system having a variety of functions and the capacity tosatisfy various specific requirements.

SUMMARY OF THE INVENTION

In view of the foregoing, it is an object of the present invention toprovide an optical transmission system constructing method capable ofeasily constructing an optical transmission method and system dependingon required functions and capacities.

Briefly, the foregoing object is accomplished in accordance with aspectsof the present invention by an optical transmission system. The opticaltransmission system is characterized in constructing a line terminalhaving multiplexing means for multiplexing signals and demultiplexingmeans for demultiplexing the multiplexed signal so that to serve as atransmitter, the line terminal is selectively capable of implementingeither of two types of converters a first combination of anelectric-to-optic converter circuit for converting the electric signalmultiplexed by the multiplexing means to a transmission light with anoptical fiber amplifier for amplifying the transmitting light beforefeeding into an optical transmission medium; or an electric-to-opticconverting means having a semiconductor optical amplifier for convertingthe electric signal multiplexed by the multiplexing means to atransmission light before feeding an optical transmission line. Theoptical transmission system also is characterized in constructing theline terminal so that to serve as a receiver, the line terminal isselectively capable of implementing either: a second combination of anoptical fiber amplifier for amplifying a receiving light from an opticaltransmission medium with an optic-to-electric converter circuit forconverting the amplified receiving light to electric signal beforefeeding to the demultiplexing means; or an optic-to-electric convertingmeans for converting the received light from the optical transmissionmedium to electric signal before feeding to the demultiplexing meanswith an avalanche photodiode used as a light receiver.

Also, the optical transmission system is characterized in constructingthe optical transmission system for use as a long distance opticaltransmission system, a plurality of the line terminals having the firstcombination to serve as the transmitter and the second combination toserve as the receiver implemented therein each are connected to theoptical transmission medium through a single or a plurality of repeatersinserted in the optical transmission medium for multiplying the opticallight signal on the optical transmission medium.

Further, the optical transmission system is characterized inconstructing the optical transmission system for use as a short distanceoptical transmission system, the plurality of the line terminals havingthe electric-to-optic converting means having a semiconductor opticalamplifier therein to serve as the transmitter and the optic-to-electricconverting means having the avalanche photodiode used as the lightreceiver to serve as the receiver implemented therein each are directlyconnected to the optical transmission line.

The optical transmission system constructing method of the presentinvention enables an easy construction of any of the long-distance andshort-distance optical transmission systems only by selecting desiredtypes of the transmitters and receivers to be implemented to change thecombinations of the units. This is because the line terminal isconstructed so that to serve as the transmitter, the line terminal isselectively capable of implementing either the first combination of anelectric-to-optic converter circuit for converting the electric signalmultiplexed by the multiplexing means to the transmission light with anoptical fiber amplifier for amplifying the transmitting light beforefeeding into an optical transmission medium or electric-to-opticconverting means having the semiconductor optical amplifier forconverting the electric signal multiplexed by the multiplexing means tothe transmission light before feeding an optical transmission line, andthat to serve as the receiver, the line terminal is selectively capableof implementing either the second combination of an optical fiberamplifier for amplifying the receiving light from an opticaltransmission medium with an optic-to-electric converter circuit forconverting the amplified receiving light to electric signal beforefeeding to the demultiplexing means or an optic-to-electric convertingmeans for converting the received light from the optical transmissionmedium to electric signal before feeding to the demultiplexing meanswith an avalanche photodiode used as light receiver.

The foregoing and other objects, advantages, manner of operation andnovel features of the present invention will be understood from thefollowing detailed description when read in connection with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram for a functional construction of an opticaltransmission system of an embodiment of the present invention.

FIG. 2 is an overall configuration for a network system related to theembodiment of FIG. 1.

FIG. 3 is a configuration for a network among a large-scale switchingnodes extracted from the network system of FIG. 2.

FIG. 4 is a configuration for a network among small-scale switchingnodes and among a small-scale switching nodes and the large scaleswitching node extracted from the network system.

FIG. 5 is a configuration for a network for a metropolitan areaextracted from the network system.

FIG. 6 is block diagrams for a functional construction of a node.

FIG. 7 is a hierarchical construction of a network system.

FIG. 8 is a frame construction for a multiplexing frame used in thenetwork system.

FIG. 9 is logical positions of path groups.

FIG. 10 is a bit allocation of overhead of the path groups.

FIG. 11 is an example of setting the path group in a ring.

FIG. 12 shows path group switching procedures at failure.

FIG. 13 shows a typical sequence of switching requests.

FIG. 14 is a block diagram for a configuration of the network systemrelated to the embodiment.

FIG. 15 is a sequence diagram for transfer of alarms in the networksystem.

FIG. 16 is a block diagram for the optical transmission system for along distance system.

FIG. 17 is a block diagram for the optical transmission system for ashort distance system.

FIG. 18 is a block diagram for a clock transit system for the opticaltransmission system.

FIG. 19 is bytes to be scrambled of an overhead in a STM-64 section.

FIG. 20 is a block diagram for the 1R-REP.

FIG. 21 is a block diagram for a board construction of the 1R-REP.

FIG. 22 is a format for a surveillance and control signal for use in thesurveillance and control of the 1R-REP.

FIG. 23 is a block diagram for an inter-office transmission lineinterface of the LT-MUX.

FIG. 24 is a block diagram for the intra-office transmission lineinterface of the LT-MUX.

FIG. 25 is a relationship of multiplex and demultiplex between a STM-64frame and a STM-1×64 supported by the LT-MUX.

FIG. 26 is a block diagram for a transmitter of the LT-MUX forming thelong distance system.

FIG. 27 is a block diagram for the transmitter of the LT-MUX forming theshort distance system.

FIG. 28 is a block diagram for a receiver of the LT-MUX forming the longdistance system.

FIG. 29 is a block diagram for the receiver of the LT-MUX forming theshort distance system.

FIG. 30 is a block diagram for a node having LT-MUXes and an ADM switchused.

FIG. 31 is a block diagram for extracted parts serving to thesurveillance and control system for the LT-MUX.

FIG. 32 lists features of the functional blocks of the surveillance andcontrol system.

FIG. 33 is a block diagram for a redundancy configuration of atransmitting system in the LT-MUX.

FIG. 34 is a block diagram for the redundancy configuration of areceiving system in the LT-MUX.

FIG. 35 is a block diagram for construction of a hitless switchingprocess feature section for transmission line.

FIG. 36 is a block diagram for a construction of a 3R-REP.

FIG. 37 is a front view for an implementation of the 1R-REP.

FIG. 38 is structures of a optical preamplifier and optical boosteramplifier forming a single 1R-REP system.

FIG. 39 is a front view for an implementation of the LT-MUX.

FIG. 40 is a front view for an implementation of two systems of theLT-MUX in a single rack without the line redundancy configuration.

FIG. 41 is a front view for an implementation of the LT-MUX forconstructing the small scale switching node with a 40G switch unit builtin as shown in FIG. 6b.

FIG. 42 is a structural view for a 40G switch.

FIG. 43 is a front view of an implementation of the LT-MUX forconstructing the large scale switching node.

FIG. 44 is a front view of an implementation of the 3R-REP.

DETAILED DESCRIPTION OF THE INVENTION

The following describes an embodiment according to the present inventionfor the optical transmission system by reference to the accompanyingdrawings.

1. General Description

First, this section outlines the optical transmission system of theembodiment.

FIG. 1 is a block diagram for the functional construction of the opticaltransmission system of the embodiment.

The optical transmission system, as shown in FIG. 1a, is an ultra-longdistance transmission system for making optical transmission betweenline terminals with multiplexers (hereinafter referred to as theLT-MUX 1) or between the LT-MUX 1 and a regenerator (hereinafterreferred to as the 3R-REP 3) with use of an optical amplifier repeater(hereinafter referred to as the 1R-REP 2). The system can send the dataat 10 Gb/sec through an optical fiber 40 up to 320 km by the 3R-REP 3 atthe longest intervals of 80 km by the 1R-REP 2.

The LT-MUX 1 makes a multiplex and section-termination-process (12) ofthe data received by an intra-office interface 11 provided therein, andconverts them to an optical signal (13). An optical booster amplifier 14magnifies the optical signal before feeding it into an opticaltransmission medium. On the contrary, the data received from the opticaltransmission medium is magnified by an optical pre-amplifier 15 beforebeing converted to an electrical signal (16). The signal then isdemultiplexed and section-termination-processed (12) before beingdistributed to the intra-office interfaces 11. The 1R-REP 2 repeats theoptical signal in a way that any of optical fiber amplifiers 21 and 22magnifies the optical signal received from the optical transmissionmedium before feeding it out. The 3R-REP 3 regenerates the data torepeat in a way that the data received from the optical transmissionmedium are magnified by an optical pre-amplifier 35 before beingconverted to electrical signal (36). The electrical signal then isdemultiplexed and section-termination-processed (32) and is multiplexedand section-termination-processed (32) again. It further is converted tooptical signal (33) and magnified by an optical booster amplifier 34before being fed into the optical transmission medium.

The interface of any equipment with the optical transmission medium(hereinafter referred to as the inter-office interface) is equivalent tothe CCITT recommended synchronous transport modulelevel N (STM-N) whereN=64, and uses a scrambled binary NRZ (non-return to zero) astransmission line code. A spectrum broading is used to prevent astimulated Brillouin scattering due to a higher power output. Theintra-office interface 11 of the LT-MUX 1 can contain a series of STM-1(150 Mb/sec) by 64 or a series of STM-4 (600 Mb/sec) by 16. (--Note thatthe series of STM-4 (600 Mb/sec) by 1 can be compatible with the seriesof STM-1 by 4--).

The optical transmission system can be configured in another way 20 thatinstead of the 1R-REP 2 shown in FIG. 1a, the LT-MUXes 1 are directlyconnected together or the LT-MUX 1 is directly connected with the 3R-REP3. In this case, the transmission distance is up to 120 km withoutrepeater.

Also, the optical transmission system can be configured in still anotherway such as that shown in FIG. 1b, the 1R-REP 2, the optical boosteramplifier 14, and the optical preamplifier 15 are omitted, but LT-MUXes1 laving an opto-electric converter 2010 and an electro-optic converter2000 which are different in the characteristics from those of the LT-MUX1 in FIG. 1a are directly connected together. In this case, the outputlevel is around +6 dBm, and the transmission distance is up to 80 kmwithout repeater.

The optical transmission system having the LT-MUX 1, the 3R-REP 3, theoptical booster amplifier 14, and optical preamplifier 15 is called thelong-distance system hereunder; and the optical transmission systemhaving no optical booster amplifier 14 and optical preamplifier 15 inthe LT-MUX 1 and 3R-REP 3 is called the short distance system hereunder.

2. Overall System Configuration

In turn, this section describes a network system having the opticaltransmission system of the embodiment.

FIG. 2 is an overall configuration for a network system related to theembodiment.

In the figure are indicated a large scale switching node 110 having theLT-MUX 1 of the embodiment and a small scale switching node 120 havingthe LT-MUX 1 of the embodiment.

The large-scale switching nodes 110 in the network system related to theembodiment, as shown in the figure, are directly connected therebetweenin a ladder-shaped structure with use of the 1R-REP 2 and the 3R-REP 3.The network system has routes diversed therein and the CCITT recommendedVC-3/4 path protection switch in the meshed network, thereby increasingreliability of the network. The small-scale switching nodes 120 are ringstructured, and the small-scale switching nodes 120 and the large scaleswitching nodes 110 are also ring-structured. This does not only providea multiplexing effect that allows efficient use of the large-capacitytransmission medium, but also keeps two routes that can increase thereliability. In addition, a metropolitan area 130 has a multipicity ofrings for increasing the reliability in a relatively narrow, but large,area extending in a flat wide area.

FIG. 3 is a configuration for a network among the large-scale switchingnodes 110 extracted from the network system.

The large-scale switching nodes 110, as shown in the figure, aredirectly connected there among with use of the 1R-REPs 2 and the 3R-REPs3 without switching through an intermediate node, thereby decreasing theline cost. A distance between the 1R-REPs 2 is designed up to 80 kmtaking into account the S/N ratio and the distance between one of the3RREPs 3 and the mode is designed up to 320 km in consideration of thenonlinear distortion of the optical fiber.

FIG. 4 is a configuration for a network among the small-scale switchingnodes 120 and among the small-scale switching nodes 120 and the largescale switching nodes 110 extracted from the network system.

If a distance between the small-scale switching nodes 120 is shorterthan 120 km, as shown in the figure, no repeaters are used, and insteaddirect connection is made between any two of the smallscale switchingnodes 120. If the distance exceeds 120 km, the 1R-REP 2 is used to makethe long distance system as mentioned previously. If the distance isshorter than 80 km, as will be described in detail later, the 10 Gb/sectransmitter is replaced by the one made up of a semiconductor opticalamplifier and an APD (avalanche photodiode) to form a further economicshort distance system (FIG. 1b).

FIG. 5 is a configuration for a network for the metropolitan areaextracted from the network system.

The metropolitan area, as shown in the figure, has a plurality ofadjoining rings formed of the transmission media connecting the nodes ina meshed network, thereby accomplishing efficient multiplex operationand high reliability. It should be noted that there will be a greaternumber of the shorter node distances than 80 km. Then, as describedabove, the short distance system is made up of the semiconductor opticalamplifier and the APD to form the network at low cost.

FIG. 6 is block diagrams for the functional construction of the node.

The large scale switching node 110, as shown in FIG. 6a, has twoLT-MUXes 1 and a VC-3/4 cross-connection switch 111 for path switchingand setting at the VC-3/4 level in the synchronous digital hierarchy(SDH). The two LT-MUXes 1 are connected by a high-speed interface whichwill be described later, but not any intra-office interface. The largescale switching node 110 also has the STM-1 interface and the STM-4interface as the intra-office interfaces. These interfaces can connect aline repeater terminal 5000 for transmission between a 600 Mb/sec or 2.4Gb/sec offices, a cross-connection equipment 5100 for terminating theintra-office interface 11, and an ATM cross-connection switch 5200. TheATM cross-connection switch 5200, if used, can accomplish lower cost anddecrease cell delay as the 600 Mb/sec intra-office interface is used.Note that the large scale switching node 110 can be alternatively madeup of the two LTMUXes 1 and a cross-connect equipment 111.

The small scale switching node 120 is the same as the large scaleswitching node 110 or as shown in FIG. 6b, has the LT-MUX 1 and a VC-3/4add-drop multiplex (ADM) switch. The small scale switching node 120also, like the large scale switching node 110, has the STM-1 interfaceand the STM-4 interface as the intra-office interfaces, which canconnect the line repeater terminal 5000 for transmission between a 600Mb/sec or 2.4 Gb/sec offices, the cross-connection equipment 5100 forterminating the intra-office interface 11, and the ATM cross-connectionswitch 5200.

The intra-office interface 11 of the LT-MUX 1 is used for the STM-1interface and the STM-4 interface for each node.

Table 1 shows a hierarchy of the network system and terminals at therespective hierarchy level.

                  TABLE 1                                                         ______________________________________                                        NO.   LEVEL       TERMINAL        OVERHEAD                                    ______________________________________                                        1     VC-3/4      VC-1/2 processors, and                                                                        VC-3/4 POH                                                    ATM unit                                                    2     VC-3/4 path VC-3/4 cross-connector                                                                        Z3 byte of                                        group       (virtual ring branch -                                                                        representing                                      (VC-3/4 PG) insertion point)                                                                              VC-3/4 POH                                  3     STM-64 section                                                                            LT-MUX          MSOH                                        4     Regenerator 3R-REP and LT-MUX                                                                             RSOH                                              section                                                                 5     Linear repeater                                                                           1R-REP, 3R-REP, Wavelength                                        section     LT-MUX          multiplexed                                                                   management                                                                    signal                                      ______________________________________                                    

As shown in the table, the present embodiment defines the new VC3/4 pathgroup to accomplish easy path switching upon failure of any transmissionmedium.

FIG. 8 is a frame construction for an STM-64 which is an inter-officeinterface.

The overhead for the VC-3/4 path group, as shown in the figure, is theZ3 byte of the representing VC-3/4 POH forming the VC-3/4 path group.

The following describes the path switching with use of the path group atfailure of any transmission medium.

The term "path group" as used herein denotes a set of parts within aring of the VC-3/4 path that a point of insertion into a virtual ring isequal to each other and a point of branch from the virtual ring is equalto each other. The term "virtual ring" as used herein denotes a ringextracted from the network as a part which can virtually form aring-like path. It should be noted that as shown in FIG. 9, the pathgroup is positioned between section plane and path layer in view of thenetwork layer structure.

The embodiment switches the path group when the path group is atfailure. The path group is managed with use of the Z3 byte of therepresenting VC-3/4 path overhead within the path group. FIG. 10 is abit allocation of the Z3 byte. The path group failure is detected by apath group alarm indication signal (PGAIS) defined in the Z3 byte.

Table 2 shows path switching features in the embodiment.

                  TABLE 2                                                         ______________________________________                                        NO.  ITEM         DESCRIPTION                                                 ______________________________________                                        1    Switching unit                                                                             VC-3/4 path group (set of VC-3/4 paths                                        in same route within ring)                                  2    Switching network                                                                          Virtual ring (on VC-3/4 path mesh)                               topology                                                                 3    Protection form                                                                            1 + 1 bidirectional switching (Working                                        path group and protection group are                                           turned reversely on ring.)                                  4    Switching control                                                                          Autonomous switching to ground office                            method       in ring by APS control for path group                       5    APS byte     b1 to b4 of Z3 byte path group                                                representing VC-3/4                                         6    APS protocol Conform to 1 + 1 switching protocol of                                        section APS                                                 7    Switching trigger                                                                          Path group AIS reception at path group                                        terminal point                                                                (Path group AIS bit in Z4 type = 1)                         8    Switching    VC-3/4 cross-connection switch (LT-MUX                           equipment    with XC and LT-MUX with ADM)                                9    Switch control                                                                             Switching ACM* meshed network in units                           method       of VC.                                                      ______________________________________                                         *ACM = address control memory which is a memory for controlling switches      in crossconnection unit and the like.                                    

As shown in Table 2 above, the embodiment uses an alternative meshednetwork switching to increase reliability. Controlling the meshswitching in the embodiment is the autonomous switching in units of theVC-3/4 path group virtual ring, which conforms to the section APSrecommended by CCITT.

FIG. 11 is an example of setting the path group in the ring. Theprotection path group is extended in the direction reverse to theworking one.

FIG. 12 is path group switching procedures at failure. FIG. 13 is atypical sequence of switching requests. The switching sequence, as shownin FIG. 13, conforms to the usual 1+1 section APS. Finally, Table 3shows priorities of the switching requests and coding of the Z3 byte,and Table 4 shows coding of the path group status.

                  TABLE 3                                                         ______________________________________                                        PRI- TYPE OF                                                                  OR-  SWITCHING                     Z3 BYTE                                    ITY  REQUEST     DESCRIPTION       b1,b2,b3,b4                                ______________________________________                                        1    Lockout     Inhibit all switchings by any                                                                   --                                                          of following switching                                                        requests, with working state                                                  held.                                                        2    Forced switching                                                                          Make switching if protection                                                                    1 1 1 0                                         (FS)        path group is normal.                                        3    Signal failure                                                                            Make switching if protection                                                                    1 1 0 0                                         (SF)        path group is normal after                                                    results of surveillance of                                                    working path group AIS and                                                    units are triggered for                                                       failure. Path group AIS is                                                    generated by LOS, LOF, and                                                    severed MER.                                                 4    Manual switching                                                                          Make switching if protection                                                                    1 0 0 0                                                     path group is normal.                                        5    Wait to restore                                                                           Do not release from switched                                                                    0 1 1 0                                                     state during the waiting                                                      period even if the working                                                    path group is restored                                                        while the automatic switching                                                 SF or SD is made.                                            6    Exerciser   Test switching control system.                                                                  0 1 0 0                                    7    Reverse request                                                                           Respond operation of switching                                                                  0 0 1 0                                                     to requesting source after                                                    receiving request for forced                                                  switching or signal failure                                                   or wait to restore.                                          8    No bridge   Inhibit all switchings by any                                                                   0 0 0 0                                         required    of the following switching                                                    requests, with the working                                                    state held.                                                  ______________________________________                                    

                  TABLE 4                                                         ______________________________________                                        Z3 BYTE                                                                       b7, b8             DESCRIPTION                                                ______________________________________                                        0 0                Normal state                                               1 1                PG-AIS*                                                    1 0                PG-FERF                                                    ______________________________________                                         *PG-AIS = path group AIS.                                                

3. Surveillance and Control System

This section describes a surveillance and control system for the networksystem related to the embodiment.

FIG. 14 is a block diagram for a configuration of the network systemrelated to the embodiment.

Each of the LT-MUXes and the 1R/3R-REPS 2,3 has a surveillance andcontrol function 1001 and an OpS-IF 1002 for connection with an OpS(operation system) 1000. The surveillance and control are made undercontrol of the OpS 1000 which governs the surveillance and control ofthe system.

The embodiment makes a wavelength multiplex of a surveillance andcontrol signal with a main signal on the STM-64 interface beforetransmitting the multiplexed signal to monitor and control the1R/3R-REPs 2,3 having no OpS IF 1002 remotely. That is, the OpS 1000gives a direction signal to the equipment having the OpS IF 1002 to makethe equipment superimpose the direction signal onto the surveillance andcontrol signal, or makes the 1R/3R-REP having no OpS IF 1002 transfer analarm detected or generated by the 1R/3R-REP to the equipment having theOpS IF 1002. Alternatively, it can be made that the 1R/3R-REP shouldhave the OpS IF 1002 to allow the OpS 1000 to monitor and control the1R/3R-REP directly.

In turn, the surveillance and control signal of 384 kb/sec istransferred by a light of the same 1.48 μm wavelength as that of apumping light source of the 1R-REP 2. The surveillance and controlsignal, as shown in FIG. 22, also has a 48 byte frame length for a 1msec frame period, 24 bytes (192 kb/sec) of which are allocated to a DCC(data communication channel) for the remote control, 8 bytes (64 kb/sec)for an order wire, and 6 bytes (48 kb/sec) for the alarm transfer. Thesurveillance and control signal allows each of the 1R/3R-REPs 2,3 toinform the state and alarm. That is, each of the 1R/3R-REPs can generateits own monitoring information and repeat the surveillance and controlsignal generated by the preceding 1R/3R-REP as well. The statemonitoring is made at intervals of 1 sec so that an access collisioncannot happen even if, number of the 1R/3RREPs is around 100.

Also the surveillance and control signal has 1 byte allocated there tothe 1R-REP section that has a feature equivalent to that of the usualAIS. The 1R/3R-REP having detected a fatal failure, such as loss of themain signal, transfers its own ID to the succeeding repeater using theone byte. This IR/3R-REP 2,3 repeats the one byte to the LT-MUX 1. Thisallows informing of the 1R/3R-REP section AIS at intervals of 1 msec. Ifit is used, the 3R-REP converts it to an S-AIS (section alarm indicationsignal).

The features of the surveillance and control system are charted inTables 5 and 6. Surveillance and control items are charted in Table 7.

                  TABLE 5                                                         ______________________________________                                        ITEM      DESCRIPTION          NOTE                                           ______________________________________                                        Surveillance                                                                          (1)   LT-MUX               1R/3R-REP                                  and control   Has OpS-IF and is started by direction                                                             can have                                   equipment     by OpS.              OpS-IF.                                            (2)   1R-REP                                                                        Has RMT-IFs, such as DCC-IF and                                               ALARM-IF, and is started by direction                                         by surveillance and control signal.                                     (3)   3R-REP                                                                        Same as 1R-REP.                                                 Surveillance                                                                          (1)   Physical characteristics                                                                           Frame                                      and control   Frame length: 48 bytes.                                                                            synchro-                                   signal        Frame period: 1 msec.                                                                              nization                                                 Rate: 384 kb/sec.    by CMI                                                   Wavelength: 1.48 μm.                                                                            code rule                                                Line code: CMI.      violation.                                         (2)   Generation method                                                             Generation by LT-MUX and                                                      1R/3R-REP.                                                              (3)   Transfer method                                                               Is wavelength-multiplexed with the                                            main signal before being transferred.                                         1R/3R-REP determines either repeat or                                         reception with destination ID added on                                        surveillance and control signal.                                              For repeat, 1R/3R-REP stores it in                                            the reception buffer before transmis-                                         sion                                                                    (4)   Access to 1R/3R-REP  To increase                                              Access can be made from either west or                                                             reliability.                                             east.                                                           Monitoring                                                                            (1)   Amount of information:                                                                             Equivalent                                 method        4 bytes of surveillance and control                                                                to feature                                               signal.              of SONET                                           (2)   Monitoring interval/alarm transfer                                                                 F1 byte.                                                 interval: 1 sec.                                                              However, if fatal failure, such as                                            loss of signal, is detected,                                                  1R/3R-REP section AIS is transferred                                          at intervals of 1 msec.                                                 (3)   Transference can be made to either                                            west and east.                                                  ______________________________________                                    

                  TABLE 6                                                         ______________________________________                                        ITEM       DESCRIPTION        NOTE                                            ______________________________________                                        Control  (1)   Surveillance and control signal                                                                  Setting can                                 method         has DCC area of 24 bytes                                                                         be made also                                               (equivalent to 192 kb/sec)                                                                       from OpS if                                                provided therein for setting                                                                     necessary                                                  surveillance and control items.                                         (2)   Surveillance and control signal                                               has order wire area of 8 bytes                                                (equivalent to 64 kb/sec)                                                     provided therein. This allows                                                 maintenance communication.                                              (3)   Access can be made from either                                                west or east.                                                           (4)   Response is made after                                                        execution of instruction.                                      ______________________________________                                    

                                      TABLE 7                                     __________________________________________________________________________     ##STR1##                                                                      ##STR2##                                                                      ##STR3##                                                                     __________________________________________________________________________

As shown in FIG. 7, if any of the monitoring items is at failure, theequipment transfers the alarm. The alarm detection and transfer are madefor the four layers, including the 1R section layer, the 3R sectionlayer, the LT section layer, and the path layer.

The 1R section layer deals with any of the alarms detected by the 1R-REP2. The alarm is transferred by the surveillance and control signal. The1R section layer processes the following items.

(a) Optical fiber disconnection: The main signal input and thesurveillance and control signal input are disconnected by an opticalfiber disconnection.

(b) Loss of main signal: The main signal input is lost by a preceding1R/3R-REP stage failure.

(c) Loss of surveillance and control signal: The main signal input islost by a preceding 1R/3R-REP stage failure.

(d) Surveillance and control signal LOF (loss of frame): The framesynchronization surveillance and control signal is lost.

(e) Surveillance and control signal FCS (frame check sequence) error: Acode error is detected by checking the FCS of the surveillance andcontrol signal.

(f) 1R section failure REP identification: The 1R-REP having detected afatal failure writes its own ID into a predetermined byte provided inthe surveillance and control signal before generating the surveillanceand control signal. This accomplishes the feature of F1 byte for the SDHrecommended by the CCITT.

The 3R section layer performs processes about an RSOH (regeneratorsection overhead) of the STM frame.

(a) Main signal LOF: Loss of frame of the main signal is detected withA1 and A2 bytes.

(b) Error rate degradation: MER and ERR MON are generated with use of B1byte.

(c) F1 byte process: If it detects a fatal failure, the 3R-REP writesits own ID into the F1 byte of the sending STM frame. Also, if itreceives the surveillance and control signal indicating that thepreceding the 1R-REP is at failure, the 3RREP writes the ID in apredetermined byte into the F1 byte of the sending STM frame.

(d) S-AIS detection, generation, and transfer: S-AIS process is made.

The LT section layer performs processes about an MSOH (multiplex sectionoverhead) of the STM frame.

The path layer performs processes about a VC-3/4 POH (path overhead) ofthe STM frame.

In turn, the alarm of the 1R section is sent to the LT-MUX through1R-REP and 3R-REP by the surveillance and control signal.

For any of the fatal failures, such as loss of the main signal, if thealarm is transferred through the 3R-REP, then the 3R-REP converts it toS-AIS. FIG. 15 is a sequence diagram for transfer of the alarm in thenetwork system.

4. Optical Transmission System

This section describes an optical transmission method for the opticaltransmission system related to the embodiment.

FIG. 16 is a block diagram for the optical transmission system for thelong distance system.

As shown in the figure, the embodiment includes a modulator integratedlight source module 200 of 1552 nm wavelength having little chirping asa sending light source for the LT-MUX 1 and the 3RREP 3. To suppress anSBS (stimulated Brillojun scattering) caused in the optical fiber, theembodiment uses the spectrum broading that a signal of a low-frequencyoscillator 201 is applied to a laser section of the modulator integratedlight source module 200 to make a light frequency modulation. Opticalbooster amplifiers 14 and 34 use a bidirection pumping method for whicha pumping light source of 1480 nm wavelength is used. The transmissionpower and chirping quantities of a modulator are optimized to accomplishthe longest regeneration distance of 320 km.

To transmit the supervisory signal, a supervision light source 202 of1480 nm wavelength range provided in the optical booster amplifier isused. The supervisory signal is wavelength multiplexed with the mainsignal before being transmitted downstream. To prevent output of thelight booster from decreasing, a WDM (wave division multiplex) coupler203 for wavelength multiplex of the surveillance and control signal withthe main signal is made to also serve as WDM coupler for laser pumping.

A forward pumping optical pre-amplifier 15,35 having a pumping source of1480 nm range accomplishes highly sensitive reception.

On the other hand, to receive the supervisory signal, a WDM coupler 210for pumping Erbium-doped fiber is used to detect the supervisory signal,which is received by an exclusive receiver. This minimizes degradationof the NF (noise figure). With the use of the light booster amplifiers14,34 and light pre-amplifiers 5,35, the distance between the LT-MUX 1and the 3R-REP 3 can be made 120 km if they are directly connectedtogether.

The 1R-REP 2 has two Erbium-doped fibers 211 and 216 and pumping lightsources of 1480 nm wavelength range used therein. The former laserpumping stage 212 pumps forward, and the latter three laser pumpingstages 213, 214, and 215 pump bidirectionally. This accomplishes bothlower NF and higher output power. For reception of the supervisorysignal by the IR-REP a WDM coupler 217 for pumping the firstErbium-doped fiber 211 stage is used to detect the supervisory signalfor an exclusive receiver 218. This minimizes degradation of the NFbelow 0.2 dB to accomplish an optimum reception of the supervisorysignal.

For transmission of the supervisory signal by the 1R-REP 2, a lightsource 219 of 1480 nm wavelength range for the supervisory signal isused to wavelength-multiplex with the main signal before beingtransmitted to a downstream. Wavelength multiplexing of the supervisorysignal with the main signal is made by using a WDM coupler 220 whichalso serves to pump the latter Erbium-doped fiber 216.

To prevent output of the light booster from decreasing, the WDM (wavedivision multiplex) coupler 203 for wavelength multiplex of thesurveillance and control signal with the main signal is made to alsoserve as the WDM coupler for laser pumping. In such a way as describedabove, with the surveillance and control signal demultiplexed andmultiplexed at the input and the output of the 1R-REP 2 respectively, aninter-office cable connected to the equipment can be used to inform afailure to the downstream even if the failure is the input signaldisconnection or in the transmission medium within the 1R-REP 2.

FIG. 17 is a block diagram for the optical transmission system for ashort distance system.

The short distance system, as shown in the figure, like the longdistance system, uses a modulator integrated light source module 200 of1552 nm wavelength for a transmitting light source. The short distancesystem is different from the long distance system in that a transmitterof the short distance system uses a semiconductor light amplifier 230 asan optical booster to make the transmitter small, and a receiver uses anoptical receiver 231 of small size and low power consumption having asuperlattice APD of low noise and wide frequency response.

If it has a high optical power input thereto, the optical fiber has anSBS caused, resulting in degradation of the transmissioncharacteristics. For the CW light, the SBS is caused with the opticalfiber input power higher than +6 dBm. In modulation, the SBS is causedby blight-line spectra contained in the signal light. It is generated ata light power level higher than the one for the CW light.

To suppress the SBS, the embodiment uses a way that the generated laserlight is modulated with a low frequency signal to broaden the lightspectra equivalently. The suppression of the SBS by broadening the lightspectra is described in an article entitled "Suppression of StimulatedBrillojun scattering and Brillojun Crosstalk by Frequency SweepingSpread-Spectrum Scheme," Journal Optical Communications, Vol. 12, No. 3,pp. 82-85 (1991), A. Hirose, Y. Takushima, and T. Okoshi.

FIG. 18 is a block diagram for a clock transit system for the opticaltransmission system.

A clock for process of section overhead of transit signals in the LT-MUX1 and 3R-REP 3, as shown in the figure, is an extracted clock smoothedby a PLL. The PLL has a time constant which is set in an order of msecthat can almost completely suppress random jitters superimposed throughthe transmission circuit and line. A low-speed wander of thetransmission clock is transferred by a pointer justification feature ofthe section overhead. With these, the 3R-REP 3 can make the repeatwithout accumulation of the jitters, so that it is free of the jitteraccumulation due to continuation of an identical code.

In transmission of the SDH section overhead, all the section overheadbytes except parts of the first line are scrambled. (FIG. 19 shows theparts of the first line, including 4 bytes containing the last 2 A1bytes and first 2 A2 bytes, 64 C1 bytes, and succeeding 2×64 fixedbytes.) This prevents repetition of a fixed pattern as much as hundredsof bytes, reduces a pattern jitter, and averages output of a timingfilter. If a 4-byte synchronous pattern is used, a frame synchronizationprotection is longer than 10 years in average misframe interval for fiveconsecutive forward protection, and is lower than 1% in misframeprobability and rehunting probability for two consecutive backwardprotection.

5. Description of 1R-REP

This section describes the 1R-REP 2.

FIG. 20 is a block diagram for the 1R-REP. Table 8 charts major featuresof the 1R-REP 2.

                  TABLE 8                                                         ______________________________________                                        ITEM             DESCRIPTION                                                  ______________________________________                                        Main signal                                                                           Signal wavelength                                                                          1.552 μm ± 0.001 μm                             interface                                                                             Mean light output                                                                          +10 to +12 dBm                                                   Input light level                                                                          -18 to 0 dBm                                                     Noise figure Lower than 7 dB                                                  Pumping method                                                                             Bidirectional pumping of                                                      Erubium-doped fiber, with                                                     1.48 μm pumping lasers.                               Surveillance and control                                                                       Transference of surveillance                                 method           and control signal by 1.48 μm                                              wavelength multiplex.                                                         Implementation of                                                             surveillance and control                                                      section in main signal unit.                                 Physical implementation                                                                        300 mm high × 3 shelves per bay                        method           (1800 × 795 × 600 mm)                            Cooling method   Natural convection, with                                                      convection guiding plate of                                                   100 mm high.                                                 Accommodation of systems                                                                       Two systems per shelf (one                                                    system contains both east and                                                 west systems)                                                Environmental conditions                                                                       Temperature: 10 to 40° C.                                              Humidity: 20 to 80%                                          Input power condition                                                                          -42 to -53 V                                                 ______________________________________                                    

As shown in FIG. 20, the 1R-REP optical transmission system consists oftwo amplifier stages, including an optical preamplifier 301 formagnification with a low noise and an optical booster amplifier 320 forhigh power magnification. An output of the optical preamplifier 301 isconnected to an input of the optical booster amplifier 320. Thisaccomplishes a low noise, high power output characteristic in a widedynamic range.

Description of the preamplifiers is ignored here as it was already madepreviously by reference to FIG. 16.

The 1R-REP 2 can monitor light outputs and intermediate signal powersand detect opening of the outputs so that it can control and monitor again of each optical amplifier stage. As described previously, the1R-REP 2 also can receive and transmit the surveillance and controlsignal of 1.48 μm wavelength. The monitor and control and processing ofthe surveillance and control signal are made by a supervisory signalprocessor/automatic power control circuit 310.

FIG. 21 is a block diagram for a package construction of the 1R-REP 2.The main signal system of the 1R-REP 2, as shown in the figure,comprises two packages, including a preamplifier package having thelow-noise optical pre-amplifier 301 and a booster amplifier packagehaving the high-power optical booster amplifier 320. As will bedescribed later, a single bay having a plurality of shelves, each ofwhich has two systems and the OpS IF as a common section.

The ground 1R-REP 2, like the LT-MUX 1 and the 3R-REP 3, has features ofpreventive maintenance, failure identification, and workabilityincrease.

These features facilitate troubleshooting for each 1R repeater section.As for the 1R repeater section overhead providing a feature of asurveillance and control communication channel between offices havingthe 1R-REP 2, as described previously, it uses the surveillance andcontrol light of 1.48 μm wavelength.

The following describes monitor of the 1R repeater section and processof the 1.48 μm surveillance and control signal in detail. It should benoted that the surveillance and control made by the 1R-REP 2 aresimilarly made by the LT-MUX 1 and the forward pumping opticalpre-amplifier 35 and the optical booster amplifier 34 of the 3R-REP 3.

Table 9 lists surveillance and control items of the 1R-REP 2.

                  TABLE 9                                                         ______________________________________                                        Surveillance                                                                          Alarm    Signal    Optical fiber disconnection                                         failure   Main signal (Preceding REP                                                    failure)                                                                      Loss of surveillance and                                                      control signal (Preceding REP                                                 failure)                                                                      Surveillance and control                                                      signal LOF (CMI)                                                              Surveillance and control                                                      signal FCS (frame check                                                       sequence) error                                                     Equipment Output open                                                         failure   Main signal transmit failure                                                  Surveillance and control                                                      signal transmit failure                                                       Optical amplifier equipment                                                   failure                                                                       Surveillance and control                                                      equipment failure                                                             Power source system failure                        Monitor      Input signal level                                                            Intermediate signal level                                                     Output signal level                                                           Pumping LD temperature                                                        Pumping LD bias                                                               Surveillance and control LD temperature                                       Surveillance and control LD bias                                              Gain                                                             Control Year and date setting and reading                                             Output halt and release                                                       Failure section determination                                         ______________________________________                                    

As shown in FIG. 9, the 1R-REP 2 provides the following processes withuse of surveillance lights and control signals marked with an encirclednumber in FIG. 20.

Number 1 in FIG. 20 denotes a surveillance light signal which is takenby a PF-WDM out of the input light having been composed of the mainsignal light of 1552 nm wavelength and the surveillance and controllight signal of 1480 nm wavelength. The surveillance light signal is3R-processed and converted to an electrical signal by a supervisorysignal receiver. The surveillance light signal is used by the automaticpower control circuit surveillance signal processor 310 to detect thesupervisory signal input disconnection.

Number 2 in FIG. 20 denotes a monitor light branched from a light outputof the low-noise amplifier section by a CPL. The monitor light is usedby the automatic power control circuit surveillance signal processor 310to control the gain, to monitor the input state, and to monitor theintermediate power.

Number 3 in FIG. 20 denotes another monitor light branched from a lightoutput of the high-power output amplifier section by another CPL. Thismonitor light is taken out through a BPF. The monitor light is used bythe automatic power control circuit surveillance signal processor 310 tocontrol the gain and to monitor the output state.

Number 4 in FIG. 20 denotes still another monitor light branched throughthe CPL from a light reflected from the output end. This monitor lightis used by the automatic power control circuit surveillance signalprocessor 310 to detect opening of the output.

Number 5 in FIG. 20 denotes control signals used by the automatic powercontrol circuit surveillance signal processor 310 forstabilization-control of the output of the pumping source and to monitorLD states.

Number 1 in FIG. 20 denotes the surveillance and control signal sentfrom the automatic power control circuit surveillance signal processor310. The surveillance and control signal is converted to an opticalsignal by the surveillance and control light source of 1480 μmwavelength. The optical signal is composed with the light output of thehigh-power output amplifier by the BB-WDM. The surveillance and controlsignal is used to monitor the surveillance light source LD state and todetect the supervisory signal transmit failure.

It is needed for the 1R-REP 2 that depending on the surveillance resultsand the like of the surveillance items, as described above,identification should be made for the transmission line alarms as toloss of the main signal, transmit failure of the main signal, loss ofthe supervisory signal, the input fiber disconnection, and the like.Such failure points can be identified by a judgement logic comprehendedof the surveillance items 1, 2, and 3. Also, the 1R-REP 2 can detect theequipment failures of the optical amplifier repeater section forpreventive maintenance of equipment. Further, the 1R-REP 2 has externalcontrol features of output shutdown for safe work.

Furthermore, the 1R-REP 2, as described above, can not only send thesurveillance and control information to the downstream equipmentdepending on the surveillance results of the surveillance and controlitems, but can also repeat to transfer to the downstream equipment thesurveillance and control information received from the upstreamequipment.

Still furthermore, the embodiment does not only inform any of thefailures of the 1R-REP 2 to the downstream, but also facilitatesjudgement of a failure point in each of the 1R repeater sections andalso maintains on the inter-office fiber the surveillance and controlcommunication channel between the office having the 1RREP 2. To dothese, the surveillance and control signal light is terminated once foreach 1R-REP 2 before being repeated to the downstream through automaticpower control circuit surveillance signal processor 310 to transfer.This has the advantage that the surveillance information can betransferred by a single wavelength even if the number of repeaters isincreased.

In turn, if the wavelength used for the supervisory signal is out of therange of the optical amplifier, this will not cause saturation in theoptical amplifier, and thus will not affect the main signal. For thisreason, the light of 1.48 μm is used as described above. This lightprovides minimal transmission line fiber loss of the main signalwaveform, and allows using a WDM (wave division multiplex) coupler tocompose and divide the pumping light in common.

The CMI code is used to send the surveillance and control signal. Withthe CMI code used, a dc component and zero continuation can besuppressed. Also, a frame synchronizing circuit can be made up ofrelatively few components by a frame synchronization method of codeviolation.

FIG. 22 is a format for the surveillance and control signal for use inthe surveillance and control of the 1R-REP 2.

The embodiment accomplishes the feature of remote control in a way shownin FIG. 22. The surveillance and control signal used is of a 48byte-long frame for period of 1 msec at a rate of 384 kb/sec, and theDCC of 192 kb/sec is maintained within the surveillance and controlsignal. The frame has 1 byte for information of severe failures everyperiod of 1 msec. This accomplishes the feature equivalent to the F1byte of the SDH.

6. Description of LT-MUX

This section describes the LT-MUX 1 in detail.

FIGS. 23 and 24 are block diagrams for hardware constructions of thelong distance system related to the embodiment. Table 10 charts majorfeatures of the LT-MUX 1. As for differences of the hardwareconstruction of the LT-MUX 1 for use in the short distance system fromthose of the long distance system, they will be described below asnecessary.

                  TABLE 10                                                        ______________________________________                                                DESCRIPTION                                                                     FOR LONG-DISTANCE                                                                            FOR SHORT-DISTANCE                                   ITEM      SYSTEM         SYSTEM                                               ______________________________________                                        Intra-office                                                                  interface                                                                     Transmission rate                                                                       155.52 Mb/sec (STM-1) × 64 series or                                    622.08 Mb/sec (STM-4) × 16 series.                            Transmission line                                                                       Scrambled binary NRZ.                                               code                                                                          Error rate                                                                              Lower than 10.sup.-11                                               Light source                                                                            1.31 μm + 0.05 μm to -0.04 μm (STM-1);                     wavelength                                                                              1.31 μm + 0.05 μm to -0.05 μm (STM-4)                      Average light                                                                           -17 to -11 dBm (STM-1); -15 to -8 dBm (STM-4)                       output                                                                        Maximum   Higher than -8 dBm                                                  detectable power                                                              Minimum   Lower than -24 dBm (STM-1);                                         detectable power                                                                        Lower than -23 dBm (STM-4)                                          Redundancy                                                                              1 + 1 dual                                                          configuration                                                                 Inter-office                                                                  interface                                                                     Transmission rate                                                                       9953.28 Mb/sec (equivalent to STM-64)                               Transmission line                                                                       Scrambled binary NRZ (non-return to zero)                           code                                                                          Error rate                                                                              Lower than 10.sup.-11                                               Light source                                                                            1.552 ± 0.001 μm, with chirping parameter                     wavelength                                                                              α being 1.0 ± 0.2                                          Average light                                                                           +10 to +12 dBm +5.6 to +6.6 dBm                                     output    Direct LT connection:                                                         +15 to +16 dBm                                                      Maximum   Higher than -7 dBm                                                                           Higher than -10 dBm                                  detectable power                                                              Minimum   Lower than -27 dBm                                                                           Lower than -23 dBm                                   detectable power                                                              Redundancy                                                                              Mesh switching using virtual ring at VC-3/4 level                   configuration                                                                 Surveillance and                                                                        Surveillance control by OpS interface.                              control method                                                                          1R-REP surveillance and control by 1.48 μm                                 wavelength multiplex.                                               Physical  300 mm high with 4 shelves (1800 × 795 × 600 mm)        implementation                                                                method                                                                        Cooling method                                                                          Push-pull type forced air cooling, with large fan.                  Accommodation                                                                           Two systems per rack.                                               of systems                                                                    Environmental                                                                           Temperature: 10 to 40° C.                                    conditions                                                                              Humidity: 20 to 80%                                                 Input power                                                                             -42 to -53 V                                                        condition                                                                     ______________________________________                                    

FIG. 23 is for the inter-office transmission line of the LT-MUX 1. FIG.24 is for the intra-office transmission line of the LTMUX 1. The LT-MUX1, as shown in the figures, comprises a high-speed IF shelf 600, alow-speed IF shelf 700, a supervisory control/OpS 650, an OH IF 660, anda clock section 670.

The high-speed IF shelf 600 comprises an OPTAMP S 601 having features asthe optical booster amplifier 14 of the transmitting system, an OPTAMP R603 having features as the optical pre-amplifier 15 of the receivingsystem, a 10G IF S 602, a 10G IF R 64, and a plurality of S0H 605boards. The lowspeed IF shelf 700 comprises a plurality of SELs 701, anda plurality of intra-office IF 702 packages. The high-speed IF shelf 600and the low-speed IF shelf 700 are connected together by anintra-equipment interface of 155 Mb/sec rate.

The embodiment has a high-speed interface 600-1, an SEL 701-1, and anintra-office interface 702-1 to have a redundancy feature of 1+1 sectionswitching type. These blocks are not needed if the section switching isnot made.

Tables 11 and 12 chart the features of the LT-MUX 1.

                  TABLE 11                                                        ______________________________________                                              BLOCK                                                                   ITEM  NAME      FEATURE              NOTE                                     ______________________________________                                        1     10G IF-S  (1)   Optical booster amplification                                 OPTAMP-S  (2)   1R repeater surveillance and                                                  control signal light transmission                                       (3)   STM-64 signal E/O conversion                                            (4)   10 GHz PLL                                                              (5)   STM-64 RSOH transmission                                                (6)   Physical rate conversion of                                                   155 Mb/sec to 10 Gb/sec                                 2     10G IF-R  (1)   Optical preamplification                                      OPTAMP-R  (2)   1R repeater surveillance and                                                  control signal light reception                                          (3)   STM-64 signal D/E conversion and                                              clock extraction                                                        (4)   STM-64 RSOH termination                                                 (5)   Physical rate conversion of                                                   10 Mb/sec to 155 Gb/sec                                 3     SOH       (1)   STM-64 MSOH process                                                     (2)   Pointer conversion of AU-3, AU-4,                                             and AU-4-4c                                                             (3)   POH monitor of VC-3, VC-4, and                                                VC-4-4c and line test                                   4     SEL       (1)   System 0/system 1 selection of                                                STM-1/STM-4 intra-office                                                      transmission line                                                       (2)   System 0/system 1 phase matching                                              of VC-3, VC-4, and VC-4-4c                                                    (hitless switching)                                                     (3)   APS protocol control for intra-                                               office transmission line switching                      5     Intra-IF  STM-1 or STM-4 intra-office                                                   transmission line termination                                           (1) E/O and O/E conversions                                                   (2) SOH process                                                               (3) Pointer conversion of AU-3, AU-4,                                             and AU-4-4c                                                               (4) POH monitor of VC-3, VC-4, and                                                VC-4-4c and line test                                                     Number of accommodated lines is                                               STM-1 × 8 or STM-4 × 2 per board.                       6     SVCONT    (1)   Information collection in low-speed                           (LIF)           IF shelf, operation of performance                                            surveillance information, and event                                           made of alarm data                                                            * Intra-office section                                                        * AU pathbus                                                                  * Surveillance in equipment                                             (2)   Alarm priority processing and                                                 failure determination                                                   (3)   Distribution and status reading of                                            control information in shelf                                                  * Software strap of intra-office                                              section                                                                       * AU line test                                                                * Selected status of redundancy                                               system                                                  ______________________________________                                    

                  TABLE 12                                                        ______________________________________                                              BLOCK                                                                   ITEM  NAME     FEATURE               NOTE                                     ______________________________________                                         7    SVCONT   (1)   10G high-speed transmission IF,                                (HIF)          surveillance information collection of                                        submarine repeater, operation of                                              performance surveillance infor-                                               mation, and event made of alarm data                                          * 1R repeater section                                                         * Multiplex section                                                           * AU path                                                                     * Surveillance in equipment                                             (2)   Alarm priority processing and failure                                         determination                                                           (3)   Distribution and status reading of                                            10G high-speed transmission line IF                                           and repeater control information                                              * Software strap                                                              * AU line continuity check                                                    * Control and status reading of                                               repeater                                                  8    SEMF     (1)   OpS message conversion                                                  (2)   Time management and history                                                   processing                                                              (3)   Emergency start-up of backup                                                  memory                                                                  (4)   Switching control of clock section                                            and SVCONT                                                              (5)   Processing of common system alarm                         9    OpS IF   (1)   OpS message communication                                                     processing                                               10    RMT IF   (1)   Remote surveillance and control                                               communication by DCC of multiplex                                             section overhead (MSOH)                                  11    CREC     (1)   B/U conversion of 64 kHz + 8 kHz                                              clock                                                    12    CDIS     (1)   Clock generation (PLL) and                                                    distribution in equipment                                13    CSEND    (1)   Transmission of extracted clock                          14    OH IF    (1)   Input/output of overhead signal                                               outside equipment                                                       (2)   OAM processing by overhead signal                        ______________________________________                                    

FIG. 25 is a relationship of multiplex and demultiplex between theSTM-64 frame and the STM-1×64 supported by the LT-MUX.

A 10G E/0 610 of a 10G IF S 602 and an OPTAMP S 601 form the transmitterof the LT-MUX 1, and a 10G O/E 611 of a 10G IF R 604 and an OPTAMP R 603form the receiver of the LT-MUX 1.

The following describes the transmitter and the receiver mentionedabove.

FIG. 26 is a block diagram for the transmitter of the LT-MUX 1 formingthe long distance system.

The transmitter, as described previously, comprises the 10G E/O S 610having the high-speed multiplex circuit 682 for converting a 622 Mb/sec,16-parallel signal to 9.95 Gb/sec signal in a way of a 16-bit multiplex(STM-64) and the electro-optic converter 681 and the OPTAMP S 601 whichis an optical amplifier.

As shown in the figure, the embodiment uses an external modulation ofelectric field absorption type for electro-optic conversion. The OPTAMPS 601 is formed of an optical fiber amplifier. The optical fiberamplifier is separately implemented in its respective package in view ofits occupying area and consumption power. The transmitter further has atemperature control circuit 683 and an optical output control circuit684 so that the long-distance transmission can be made even ifenvironmental conditions around the electro-optic converter 681 and theOPTAMP S 601 change. Description of the transmission operation isignored as it was already made by reference to FIG. 16.

FIG. 27 is a block diagram for the transmitter of the LT-MUX 1 formingthe short distance system.

The transmitter of the LT-MUX 1 forming the short distance system, asdescribed in the figure, has no OPTAMP S 601. The 10G IF S 602, unlikethat of the long distance system, uses a semiconductor optical amplifierof preferably smaller size and lower power consumption for opticalamplification in the 80-km transmission. The semiconductor opticalamplifier can be made to occupy as narrow an area as the modulator withLD, and can be implemented in the 10G IF S 602 shelf. The embodiment, asshown in the figure, uses a modulator of an electric field absorptiontype for the external modulator. The electric field absorption typemodulator is integrated to a module of small size as electric fieldabsorption type device are structurally practical to integrate with thelaser diode for the light source.

FIG. 28 is a block diagram for the receiver of the LT-MUX 1 forming thelong distance system.

The receiver comprises the OPTAMP R 603 which is an optical amplifierand the 10G O/E 611 having an opto-electric converter 693 and ahigh-speed demultiplex circuit 692. The OPTAMP R 630, as shown in thefigure, is made up of an optical fiber amplifier having an opticalpreamplifier feature, and is separately implemented in its respectiveboard. The opto-electric converter 693 is made up of a front module, anamplifier, a timing extractor, and an discrimination circuit. Thehighspeed demultiplex circuit 692 converts the 9.95 Gb/sec signal to 622Mb/sec in a way of parallel demultiplex. Description of the receptionoperation is ignored as it was already made by reference to FIG. 16.

FIG. 29 is a block diagram for the receiver of the LT-MUX 1 forming theshort distance system.

The short distance system is different from the long distance system inthat the short distance system has no OPTAMP R 603 and uses an APD 694for opto-electric conversion. As the APD 694 is capable of highersensitive reception than Pln-PD, the short distance system needs nooptical amplifier, thus resulting in a smaller system.

In turn, if the LT-MUX 1 and the ADM switch are combined to form thesmall scale switching node 120 as in FIG. 6, the high-speed IF shelf,the low-speed IF shelf 700, and a 40G switch shelf are combined as shownin FIG. 30. The 40G switch shelf comprises multiplexing circuits 901 formultiplexing the input signals to feed to time-division switches 903,the time-division switches 903, and demultiplexing circuits 902 fordemultiplexing the signals from the time-division switches 903. Aninterface of the multiplexing circuits 901 and the demultiplexingcircuit 902 is the intra-equipment interface.

In turn, the signal from the transmission line is processed by thehigh-speed IF shelf 600 before being directly input to the switchwithout the low-speed IF shelf 700. The signal to be dropped into theoffice, is connected to the low-speed IF shelf 700. As for the signal tobe passed to the another node, it is connected to the high-speed IFshelf 700 before being fed out to another node. That is, the signal fromthe transmission line is not converted as to interface by the lowspeedinterface before being connected to the switch, as usual.

But, the high-speed IF shelf 600 is directly connected with the switch.This can make the equipment smaller.

If the small scale switching node 120 or the large scale switching node110 is constructed to have the cross-connection switch feature, the 40Gswitch in FIG. 30 is replaced by a multi-stage switch configured of aplurality of 40G switch shelves.

As described above, the embodiment can appropriately combine thehigh-speed IF shelves 600, the low-speed IF shelves 700, and the 40Gswitch shelves 900 in the building block way. This allows accomplishmentof a desired equipment with use of the common shelves in a minimizedconstruction. Also, the embodiment allows accomplishment of the 3R-REP 3by combination of the boards of the high-speed IF shelf 600 as will bedescribed later.

The following describes the surveillance and control system for theLT-MUX 1.

FIG. 31 is a block diagram for extracted parts serving as thesurveillance and control system for the LT-MUX 1.

FIG. 32 lists features of the functional blocks.

Tables. 13, 14, 15, and 16 chart features of the surveillance andcontrol system.

In FIGS. 31 and 32, the SVCONT 703 is installed for each low-speed IFshelf. The SEMF 651, the OpS IF 652, and RMT IF 653 are equipped in thecommon a shelf as will be described later.

                  TABLE 13                                                        ______________________________________                                        FEATURE   DESCRIPTION          NOTE                                           ______________________________________                                        1   Path      (1)   Switch control memory is updated                                                               Control                                      setting         to set path according to the control                                                           system                                                       message from the operation system                                             outside equipment.                                                      (2)   Path setting units include:                                         a.  Units of VC-3                                                             b.  Units of VC-4                                                             c.  Units of VC-4c                                                                (600M at max)                                                                 (3)   This feature is an option for                                                 implementation of crossconnection                                             feature                                                   2   Software  (1)   Control register of each section in                                                            Control                                      strap           equipment is updated to set                                                                    system                                       setting         operation mode (software strap)                                                                NOTE 1:                                                      according to control message from                                                              Upon use of                                                  operation system outside                                                                       section                                                      equipment.       protection                                             (2)   Major software strap features                                                                  feature                                                      include:                                                            a.  Transference approval or                                                      inhibition of transmission                                                    line system alarm                                                         b.  Threshold of error rate                                                       degradation                                                               c.  Protection time of switching                                                  control (NOTE 1)                                                3   Path test (1)   Test access point is set to confirm                                                            Control                                                      continuity and set quality in units                                                            system                                                       of path according to the control                                              message from the operation system                                             outside equipment.                                                      (2)   Path testing units include:                                         a.  Units of VC-3                                                             b.  Units of VC-4                                                                 (3)   Test pattern conforms to CCITT                                                Recommendation 0.151                                      4   Redundancy                                                                              (1)   The operation system switches                                                                  Control                                      system          over functional components of                                                                  system                                       switching in    equipment having redundancy form                                                               Surveillance                                 equipment       according to the control message                                                               system                                                       from the operation system outside                                             equipment. (Forced switching)                                           (2)   As results of equipment diagnosis,                                            the operation system switches over                                            to the protection side from function                                          component of equipment judged at                                              failure. (Autonomous switching)                                         (3)   Operation modes of redundancy                                                 system include:                                                     a.  Automatic mode, allowing                                                      autonomous switching                                                      b.  Forced selection mode                                                     c.  Lock-out mode                                                   ______________________________________                                    

                  TABLE 14                                                        ______________________________________                                        FEATURE    DESCRIPTION         NOTE                                           ______________________________________                                        5   Configuration                                                                            (1)   Implementation states of                                                                      Surveillance                                 management       functional components of                                                                      system                                                        equipment are monitored, and                                                  the database for configuration                                                management in the control                                                     system is automatically updated                                               as needed.                                                              (2)   When the implemented                                                          functional component does not                                                 logically match with the physical                                             implementation position, then an                                              alarm is issued.                                                        (3)   Management units for functional                                               components of equipment                                                       include:                                                            a.  Board                                                                     b.  Board group                                                               c.  Shelf                                                          6   Alarm      (1)   Transmission line system alarms                                                               Surveillance                                 transference     are collected from line                                                                       system                                                        termination feature blocks                                                    and path connection feature                                                   blocks to detect generation and                                               restoration of alarms before                                                  transmission line system alarms                                               are made into an event.                                                 (2)   On basis of diagnosis results of                                              equipment failure, equipment                                                  alarms are made into an event.                                          (3)   Contents of these alarms made                                                 into a event are converted to                                                 messages before being informed                                                to external surveying operation                                               system.                                                  7   Performance                                                                              (1)   Performance information, such                                                                 Surveillance                                 management       as a bit error, are collected                                                                 system                                                        from line termination feature                                                 blocks and path connection                                                    feature blocks to calculate                                                   and generate performance                                                      management information for                                                    transmission lines and paths.                                           (2)   The performance management                                                    information includes:                                               a.  CV (code violation)                                                       b.  ES (errored second)                                                       c.  SES (severely errored                                                         second)                                                                 (3) Types of registers for history                                                management includes:                                                        a.  1-sec register                                                            b.  15-min register                                                           c.  1-day register                                                 ______________________________________                                    

                  TABLE 15                                                        ______________________________________                                        FEATURE   DESCRIPTION          NOTE                                           ______________________________________                                         7  Equipment (1)   Failure surveillance information is                                                            Surveillance                                 diagnosis       collected from functional                                                                      system                                                       components of equipment, and a                                                specific functional component                                                 having a hardware failure                                                     generated is identified on the                                                basis of the failure judgement map                                            provided in the surveillance and                                              control system.                                                         (2)   Specific functional component                                                 having a hardware failure                                                     generated is logically disconnected,                                          and the operation system switches                                             over from the functional                                                      component of redundancy                                                       configuration to the protection                                               side.                                                                   (3)   Equipment information is sent out                                             to inform existence of a functional                                           component having a failure                                                    generated.                                                 9  Section   (1)   If a section failure happens, section                                                          Control                                      switching       switching is controlled on the basis                                                           system                                       control         of MSP protocol. Surveillance                                           (2)   Switching system includes the                                                                  system                                                       following manners:                                                                             MPS:                                               a.  1 + 1 (without switch-back)                                                                    Multiplan                                                b.  Bi-directional switching                                                                       Section                                                (3) Switching is caused by include:                                                                  Protection                                               a.  SF switching (LOS, LOF,                                                       S-AIS, and hardware failure)                                              b.  SD switching (MER)                                                        c.  Forced switching                                                              (OpS command)                                                           (4) This feature is optional.                                         10  Path      (1)   If a path failure is detected with                                                             Control                                      switching       generation of a failure in the ring                                                            system                                       control         meshed network, section switching                                                              Surveillance                                                 is controlled on the basis of MSP                                                              system                                                       protocol.        PGP =                                                  (2)   Switching system includes the                                                                  Path                                                         following manners:                                                                             Group                                              a.  1 + 1 (with switch-back)                                                                       Protection                                               b.  Bilateral switching                                                     (3) Switching is "aused by include:                                             a.  SF switching (LOP, P-AIS,                                                     and hardware failure)                                                     b.  SD switching (MER)                                                        c.  Forced switching                                                              (OpS command)                                                           (4) This feature is optional for                                                  implementation of cross-                                                      connection feature.                                               ______________________________________                                    

                  TABLE 16                                                        ______________________________________                                        FEATURE     DESCRIPTION        NOTE                                           ______________________________________                                        11  History     (1)   Variety of events generated as                                                               Control                                      management        to transmission line received                                                                system                                                         signals and equipment statuses                                                               Surveillance                                                   are recorded and managed as                                                                  system                                                         history information.                                                    (2)   History information to be                                                     managed includes:                                                   a.  Redundancy system                                                             switching history                                                         b.  Signal performance                                                            history                                                                   c.  APS information                                                               changing history                                              12  Backup      (1)   If the operation state in                                                                    Control                                      information       equipment is changed, then                                                                   system                                       management        the changed state is                                                                         NOTE 1:                                                        automatically recorded in                                                                    With use of                                                    nonvolatile memory as the                                                                    cross-                                                         latest information.                                                                          connection                                               (2)   Information to be recorded                                                                   feature                                                        includes:                                                           a.  Operation information of                                                      redundancy system                                                         b.  Information of software                                                       strap                                                                     c.  Path setting information                                                      (NOTE 1)                                                                (3) The following processes are                                                   made with the control                                                         message from the control                                                      operation system                                                            a.  Update of backup                                                              information                                                               b.  Comparison with statuses                                                      in equipment                                                              c.  Initialization of backup                                                      information                                                   13  Emergency   (1)   If it is powered on, equipment                                                               Control                                      start-up          is autonomously started up for                                                               system                                                         operation on basis of backup                                                  information.                                            14  Communication                                                                             (1)   Control is made on                                                                           Control                                      control           communication with the                                                                       system                                                         operation system outside                                                                     Surveillance                                                   equipment.     system                                                   (2)   Communication is of a                                                         message form and has a                                                        protocol system on basis of                                                   the Q interface of CCITT                                                      Recommendations.                                                        (3)   Two independent                                                               communication links are                                                       provided, including the                                                       control system and                                                            surveillance system.                                    15  OpS message (1)   Control information of                                                                       Control                                      conversion        message received from                                                                        system                                                         operation system is converted                                                                Surveillance                                                   to the command form specific                                                                 system                                                         to equipment.                                                           (2)   Control information and                                                       surveillance information of                                                   the command form specific to                                                  equipment are converted to                                                    information of message form                                                   before being sent to the                                                      operation system.                                       ______________________________________                                    

FIG. 33 is a block diagram for the redundancy configuration of thetransmitting system in the LT-MUX 1. FIG. 34 is a block diagram for theredundancy configuration of the receiving system in the LT-MUX 1.

In general, operations including AU pointer conversion are nonhitlesslyswitched. To make this hitless, a hitless switching process is needed.In the embodiment, in view of the balance of the features provided inthe whole equipment, the AU pointer conversion process is provided inthe intra-office interface and the high-speed interface unit. In the SEL701 between these is provided a hitless switching process featuresection which will be described later. As shown in the figures, simplexsections are optical booster amplifier 601, 10G IF-S 602 and the SOH 605in the operation form without the 1+1 section switching in the 10 Gb/sectransmission line.

As the intra-office interface is an interface to be connected with anexisting intra-office equipment, the redundance configuration followsthe manner of the existing equipment. That is, the redundanceconfiguration is made of the 1+1 section switching type of system0/system 1 without switch-back. The board for the intra-office interfaceaccommodates a plurality of highways. Auto-switching at failure is madein units of transmission line. The intra-office interface board,therefore, has working highways and waiting highways mixed therein. Forthis reason, for interface package maintenance, a hitless forcedswitching is needed which will be described later.

The SEL 701, as shown in FIGS. 23 and 24, is arranged so that it can beadded or removed depending on the situation of transmission lineaccommodation. The SEL 701, therefore, is arranged so that it can beautomatically switched in units of package in the 1+1 way. Note that ifthe hitless forced switching which will be described later is made forthe SEL 701, this is hitlessly made by the hitless switching processsection.

Now, the following describes the hitless switching process.

FIG. 35 is a block diagram for construction of the hitless switchingprocess feature section for transmission line. Table 17 lists featuresof functional blocks of the hitless switching process feature section.

                  TABLE 17                                                        ______________________________________                                        NO.  ITEM         FEATURES                                                    ______________________________________                                         1   AU pointer   AU pointer byte and AU stuff operation are                       termination  read. It is instantaneously taken in without                                  protection of consecutive coincidence three                                   times.                                                       2   2 × 2 SEL                                                                            Selector for passing delayed system through,                                  but storing preceding system into VC buffer.                 3   VC buffer    FIFO memory for delaying preceding VC-3,                                      VC-4, and VC-4-4c data. Adjustable distance                                   difference is 4 km.                                          4   VC buffer writing                                                                          Writing address counter for VC buffer. Only                      control      VC-3, VC-4, and VC-4-4c data of input                                         signal are written according to detection of                                  AU stuff.                                                    5   VC buffer reading                                                                          VC buffer is read in line to AU stuff of the                     control      delayed system. If delay insertion is needed                                  to increase in phase synchronizing pull-in                                    course, positive stuff is added. If it is needed                              to decrease, negative stuff is added.                        6   Delay insertion                                                                            Delay insertion of FIFO is calculated through                    calculation  calculation of the writing address minus                                      reading address.                                             7   Phase difference                                                                           Transmission delay difference is detected by                     detection    comparison of AU pointer values.                             8   Delay insertion                                                                            Result of delay insertion calculation is                         control      compared with result of phase difference                                      detection. If it is necessary to increase delay                               insertion, positive stuff is added on VC                                      buffer reading side. If it is necessary to                                    decrease delay insertion, negative stuff is                                   added on the VC buffer reading side.                                          2 × 2 SEL is controlled depending on the                                direction of the delay difference generation.                9   Pointer calculation                                                                        New pointer value is calculated by                                            comparison of the VC input phase of the VC                                    buffer with output frame phase.                             10   Pointer insertion                                                                          New pointer value is written in VC buffer                                     output signal.                                                                Following specific patterns are written in                                    predetermined positions.                                                (1) On generation of stuff:                                                       Inversion of bits 1 and 0.                                                (2) On jump of pointer:                                                           Sending of NDF pattern.                                                   (3) On AU-4 or AU-4-4c:                                                           CI (concatenation indicator).                                             (4) On sending of P-AIS:                                                          All 1 of all bytes.                                           ______________________________________                                    

As depicted in Table 17, the hitless switching process feature sectionmakes the received data, including VC-3, VC-4, and VC-4-c data, of thesystem having less transmission delay of systems 0 and 1 delay in FIFOmemory (VC buffer) as necessary. This makes contents of the outputsignals of both systems coincide. Detection of the transmissiondifference is made by comparison of the pointer values. Adjustment ofthe delay insertion of the FIFO is made with stuff operation of the AUpointer so gradually that the signal of the working system will not behit while the phase synchronizing pull-in is made in maintaining theprotection system. In writing into the VC buffer, the AU pointer isterminal once before only the VC-3, VC-4, and VC-4-c data are written inthe VC buffer. In reading from the VC buffer, on the other hand, readingis made along with the operation of the AU stuff in line with that ofthe AU stuff in the delayed line. In a phase synchronized state, thus,the system 0 can be made to coincide with the system 1 perfectly notonly in the phases of the output VC signals, but also the timings of theAU stuffs. This means that the hitless switching can be made securelyeven if the frequency of the AU stuff is higher.

The VC buffer is a kind of AU pointer converting circuit. At the time ofoutput, a new AU pointer value is calculated before being inserted intothe AU. The calculation principles are the same as those of the usualpointer converting circuit. As the adjustable transmission delaydifference is 4 km, the process cannot only be applied to theintra-office transmission line, but also to a short or intermediateinter-office transmission line. Thus, in the SEL, the hitless switchingprocess feature section is constructed so that it cannot be used forswitching the intra-office interface, but also for switching the 10Gb/sec transmission line interface.

7. Description of 3R-REP

FIG. 36 is a block diagram for a construction of the 3R-REP 3. Table 18lists features of functional blocks of the 3R-REP 3.

                  TABLE 18                                                        ______________________________________                                        ITEM              DESCRIPTION                                                 ______________________________________                                        Main signal                                                                           Transmission rate                                                                           9953.28 Mb/sec (equivalent to                           interface             STM-64)                                                         Transmission line                                                                           Scrambled binary NRZ                                            code          (none-return to zero)                                           Error rate    Lower than 10.sup.-11 /repeater.                                Light source  1.552 μm ±0.001 μm                                     wavelength                                                                    Average light +10 to +12 dBm                                                  output                                                                        Maximum detectable                                                                          Higher than -7 dBm                                              power                                                                         Minimum detectable                                                                          Lower than -27 dBm                                              power                                                                 Surveillance and control method                                                                 .Surveillance and control                                                     signal transference by                                                        1.48 μm wavelength                                                         multiplexed signal.                                                           .Implementation of                                                            surveillance control section                                                  in main signal unit.                                        Physical implementation method                                                                  300 mm high with 4 shelves per                                                frame (1800 × 795 × 600 mm).                    Cooling method    Push-pull type forced air                                                     cooled type, with large fan.                                Accommodation of systems                                                                        One system per shelf, with one                                                bidirectional system of west                                                  and east.                                                   Environmental conditions                                                                        Temperature: 10 to 40° C.                                              Humidity: 20 to 80%.                                        Input power condition                                                                           -42 to -53 V                                                ______________________________________                                    

The 3R-REP 3 makes regeneration through its optical preamplification,O/E conversion, E/O conversion, and optical booster amplification. The3R-REP 3 also makes the surveillance, alarm transference, and remotemaintenance for the 1R repeater section and the 3R repeater section withuse of the 1.48 μm surveillance and control light and the RSOH(regenerator section overhead). The boards used in the main signalsystem are all the same as those of the LT-MUX 1.

8. Implementation of the 1R-REP, LT-MUX, and 3R-REP

The following describes implementation of the 1R-REP 2, LT-MUX 1, and3R-REP 3.

First, implementation of the 1R-REP 2 is described below.

FIG. 37 is a front view for an implementation of the 1R-REP 2.

A rack of the embodiment, as shown in the figure, has three shelves eachof which contains two 1R-REP 2 systems, or six 1RREP 2 systems in total.Each system comprises two subsystems: the repeaters 301 and 302. For anunattended office which needs remote monitor and control, these areimplemented in the same shelf as the system to which the OpS IF 651 andthe like serve. Note that a power source board 810 is for the opticalpreamplifier 301 and the optical booster amplifier 320.

FIG. 38 shows structures of the optical pre-amplifier 301 and opticalbooster amplifier 320 forming a single 1R-REP 2 system. The opticalpreamplifier 301 and the optical booster amplifier 320, as shown in FIG.37, occupy two-fold and four-fold widths in reference to a standardboard width respectively, or six-fold width in total. They are naturallyair-cooled. Note that a TEC drive circuit in FIG. 38 is a circuit addedto the pumping light source to control a temperature adjustment forthermoelectron cooling devices.

Implementation of the LT-MUX 1 is described below.

FIG. 39 is a front view for an implementation of the LT-MUX 1.

The construction shown is for accomplishing the transmission line 1+1redundancy system switching. The functional boards of the high-speed IFunit 600 and the low-speed IF unit 700, as shown in the figure, are alldoubled as in a working system 0 and a wailing system 1. FIG. 40 is afront view for an implementation of two systems of the LT-MUX 1 in asingle rack without the redundancy configuration.

The 10G IF R 604 package and the 10G IF S 602 board, as shown in thefigure, are of two-fold wide as these have many components. Similarly,the OPTAMP R 603 board and the OPTAMP S 601 board are of two-fold wide.

FIG. 41 is a front view for an implementation of the LT-MUX 1 forconstructing the small scale switching node 120 with the 40G switch unitbuilt in as shown in FIG. 6b.

In this case, as shown in the figure, are implemented two highspeedinterface units 600, a duplexed 40G switch unit 900, and a duplexedlow-speed IF unit 700. The 40G switch unit 900, as shown in FIG. 42, isthree-dimensionally constructed in view of the flow of its signals. Thatis, a plurality of boards MUX/DMUX containing a plurality ofmultiplex/demultiplex circuits 901 and 902 and a time-division switch(TSW) 903, are three-dimensionally connected together with use of asubpanel for a time switch unit. This construction can be made small.

Implementing the 40G switch into the shelf is made in a way that the TSW903 is put in front, the 40G switch unit 900 is put into the shelf, andthe MUX/DMUX board 901/902 is connected with other units on the rearside of the shelf.

FIG. 43a is a front view for an implementation of the LT-MUX 1 forconstructing the large scale switching node 110 with a multi-stageswitch meshed network of a plurality of the 40G switch units builttherein.

In this case, as shown in the figure, a plurality of racks have the 40Gswitch units, the high-speed IF units 600, and the lowspeed IF units 700built therein so that the high-speed IF units 600, and the low-speed IFunits 700 can be connected with the switch multi-stage network.

Finally, FIG. 44 is a front view for an implementation of the 3RREP 3.

As shown in the figure, a single rack has four shelves each of whichcontains a main signal board, including OPTAMP R 603, 10G IF R 604, 10GIF S 602, and OPTAMP S 601 packages, and a common section, such as anOpS IF 651. This construction allows a single shelf to complete all thefeatures of a single equipment. It is possible to easily increase orremove the equipment in shelf units as needed.

As described so far, the present invention can flexibly build up theoptical transmission system depending on capacities and functionrequired.

What is claimed is:
 1. An optical transmission system comprising:anoptical transmission medium connected to a plurality of line terminalsand at least a repeater connected between two of said line terminals forrepeating a main signal of a first wavelength transmitted between two ofsaid line terminals; multiplexing means in at least one of said two ofsaid line terminals, for wavelength-multiplexing said main signal with asecond signal of a second wavelength, said second signal being a signalfor surveillance or control of said main signal; monitoring means in atleast one of said repeater and said line terminals, for performing saidsurveillance or control of said main signal by use of said second signalin the wavelength-multiplexed signals; and controlling means in at leastone of said repeater and said line terminals, for controllingtransmission of said main signal by use of said second signal in thewavelength multiplexed signals, based upon the result of the monitoringperformed by said monitoring means.
 2. An optical transmission systemaccording to claim 1, wherein said repeater converts inputted lightsignal to output light signal without converting to electric signal, andsaid monitoring means in said repeater comprising:means for convertingthe second signal inputted with said wavelength-multiplexed signals, toan electric signal for performing said surveillance and control of saidmain signal; and means for converting said electric signal to an outputlight signal in the output wavelength-multiplexed signals.
 3. An opticaltransmission system comprising:An optical transmission medium connectedto a plurality of line terminals and at least a repeater connectedbetween two of said line terminals for repeating a main signal of afirst wavelength transmitted between two of said line terminals; atleast one of the two line terminals including a shelf with,a firstcircuit board slot for accommodating a first device which is anelectric-to-optic converter circuit board for converting an electricsignal to a transmission light, a second circuit board slot foraccommodating a second device which is an optic-to-electric convertercircuit board for converting received light to an electric signal,multiplexing means in at least one of said first device and said seconddevice for wavelength-multiplexing said main signal with a second signalof a second wavelength, said second signal being a signal forsurveillance or control of said main signal; a third circuit board slotfor accommodating at least one of a third device and a fourth device,said third device being a booster optical amplifier circuit board foramplifying said transmission light from said first device and saidfourth device being a pre-optical amplifier circuit board for amplifyingsaid received light before providing it to said second device;monitoring means in at least one of said repeater and said lineterminals, for performing said surveillance or control of said mainsignal by use of said second signal in the wavelength-multiplexedsignals; and controlling means in at least one of said repeater and saidline terminals, for controlling transmission of said main signal by useof said second signal in the wavelength-multiplexed signals, based uponthe result of the monitoring performed by said monitoring means.
 4. Anoptical transmission system comprising:An optical transmission mediumconnected to a plurality of line terminals and at least a repeaterconnected between two of said line terminals for repeating a main signalof a first wavelength transmitted between two of said line terminals; atleast one of the two line terminals including a shelf with,a firstcircuit board slot for accommodating a first device which is anelectric-to-optic converter circuit board for converting an electricsignal to a transmission light, a second circuit board slot foraccommodating a second device which is an optic-to-electric convertercircuit board for converting received light to an electric signal,multiplexing means in at least one of said first device and said seconddevice for wavelength-multiplexing said main signal with a second signalof a second wavelength, said second signal being a signal forsurveillance or control of said main signal; a third circuit board slotfor accommodating a third device which is a booster optical amplifiercircuit board for amplifying said transmission light from said firstdevice and a fourth circuit board slot for accommodating a fourth devicewhich is a pre-optical amplifier circuit board for amplifying saidreceived light before providing it to said second device; monitoringmeans in at least one of said repeater and said line terminals, forperforming surveillance or control of said main signal by use of saidsecond signal in the wavelength-multiplexed signals; and controllingmeans in at least one of said repeater and said line terminals, forcontrolling transmission of said main signal by use of said secondsignal in the wavelength-multiplexed signals, based upon the result ofthe monitoring performed by said monitoring means.
 5. An opticaltransmission system comprising:An optical transmission medium connectedto a plurality of line terminals and at least a repeater connectedbetween two of said line terminals for repeating a main signal of afirst wavelength transmitted between two of said line terminals; atleast one of the two line terminals including a shelf with,a firstcircuit board slot for accommodating a first device which is anelectric-to-optic converter circuit board for converting an electricsignal to a transmission light, a second circuit board slot foraccommodating a second device which is an optic-to-electric convertercircuit board for converting received light to an electric signal, athird circuit board slot for accommodating at least one of a thirddevice and a fourth device, said third device being a booster opticalamplifier circuit board for amplifying said transmission light from saidfirst device, and said fourth device being a pre-optical amplifiercircuit board for amplifying said received light before providing it tosaid second device; multiplexing means in at least one of said thirddevice and said fourth device for wavelength-multiplexing said mainsignal with a second signal of a second wavelength, said second signalbeing a signal for surveillance or control of said main signal;monitoring means in at least one of said repeater and said lineterminals, for performing said surveillance or control of said mainsignal by use of said second signal in the wavelength-multiplexedsignals; and controlling means in at least one of said repeater and saidline terminals, for controlling transmission of said main signal by useof said second signal in the wavelength-multiplexed signals, based uponthe result of the monitoring performed by said monitoring means.
 6. Anoptical transmission system comprising:An optical transmission mediumconnected to a plurality of line terminals and at least a repeaterconnected between two of said line terminals for repeating a main signalof a first wavelength transmitted between two of said line terminals; atleast one of the two line terminals including a shelf with,a firstcircuit board slot for accommodating a first device which is anelectric-to-optic converter circuit board for converting an electricsignal to a transmission light, a second circuit board slot foraccommodating a second device which is an optic-to-electric convertercircuit board for converting received light to an electric signal, athird circuit board slot for accommodating a third device which is abooster optical amplifier circuit board for amplifying said transmissionlight from said first device, and a fourth circuit board slot foraccommodating a fourth device which is a pre-optical amplifier circuitboard for amplifying said received light before providing it to saidsecond device; multiplexing means in at least one of said third deviceand said fourth device for wavelength-multiplexing said main signal witha second signal of a second wavelength, said second signal being asignal for surveillance or control of said main signal; monitoring meansin at least one of said repeater and said line terminals, for performingsurveillance or control of said main signal by use of said second signalin the wavelength-multiplexed signals; and controlling means in at leastone of said repeater and said line terminals, for controllingtransmission of said main signal by use of said second signal in thewavelength-multiplexed signals, based upon the result of the monitoringperformed by said monitoring means.